US2366232A - Multiexchange automatic telephone system - Google Patents

Description

Jan. 2. 1.945. P. BAKKER 2,366,232

-MULTIEXCHANGE AUTOMATIC TELEPHONE SYSTEM Filed-Jan. 2, 1945 4 Sheets-Sheet 1 v T @X FIG .3

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Jan. 2. 1945. P. BAKKER y y MULTIEXCHANGE AUTOMATIC TELEPHONE SYSTM Filed Jan. 2, 1945 4 Sheets-Sheet 2 Jan. 2. 1945. P, BAKKER MULTIEXCHANGE AUTOMATIC TELEPHoNEsYsTEM Filed Jan. 2, 1945 4 sheets-sheet z @EEE . JmL/en an' Fler' Bakker P. BAKKER 2,366,232

MULTIEXCHAGE AUTOMATIC TELEPHONE' SYSTEM Filed Jan. 2, 1943 4 Sheaets--Sheel'l 4 Jan. 2. 1945.y

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progresses.

, Patented Jan. 2, v1945 'MULTIEXCHANGESAUTOMATCTELEPHONE.

YSTEM Pier Baklrer, Chicago, Ill., assgnorwto Kellogg v Switchboard and Supply Company, Chicago',A K Ill., a corporation of Illinois applicati@ January 2, 1943, serialNo. 471,267.

6 claims. (c1.- lies-27) This invention relates to multi-exchange automatic telephone systems, but is concerned more particularly with4 a telephone system whereinv calls jbetween automatic telephone exchanges comprising aflocal system are handled onfa toll basis, through a local toll board, and wherein a long-distance toll board outside the local system is utilized to complete long-distance toll callsto 'and from the llines ofthe local multi-exchange system.

The principal object of the invention is the provision of suitable arrangements for thel satisfactory completion on a toll basis of all interexchange calls to and from lines of the local system.l r l v Ajspe'cic object is to provide suitable arrangements fQrtranSerring locally originated longdistance toll calls from the local toll board to the long-distance toll board. n

Aiurther specific Objectis to provide circuit arrangementsjeiective when the local toll board is not attended to-route all locally originated'toll calls to the 'long-distance toll vboard to be completed therefrom t the respective called lines, whether within or Without the local' system. Other objects and/featuresl of the invention will become more apparent asthe description General description The accompanying drawings, comprising` Figs.

l to 6, show by'means of the usual circuit diagrams a suflicient amount of the equipment in a telephone system `embodying the features of the invention to enalole'thev invention to be underv stood. 1

` Fig. l is a map-like drawing showing the exchangesof the local'system andone of the exchanges outside of the local system;

Fig. 2 shows the trunking arrangements in the exchange with which the local toll board is 'associated; i

Figs. 3 to 5 show the circuit arrangements of certain of the apparatus of Fig. 2; `and Fig. 6 is adiagram indicating how Figs. 3 to 5 are intended to be arranged.

FIGURE 1 i matic exchanges B, C, and D. Toll lines'TLA and TL interconnect exchanges C and D with tandem exchangev B. Fig. 1 `also shows an exchange A extending to still. other exchanges .outside ofv the local system, in laccordance with theI usual practice.Y 'w The local toll board LTBv may be located within exchange B, or vit may be located a short dis,-

' tance away, as intheresidence ofthe manager of the local system,fand'interconnected with the concerned equipmentinexchange Bby the required number of conductors.

. e e FIGURE l2 'y As previously stated, Fig. 2 isa diagram ci the trunking arrangement in, exchange B of Fig, 1.

`The local tollbo'ardvLTBl is indicated by a brolrenlinerectarlgleinFig, 2.l o Exchange BV is..,illustrated as having, a. present capacity of vthree hundred lines, comprising three separate hundreds groups -reached'byway ofthe Fig. 1 shows the local system comprising-autov frstthree levels respectivelyof a-.singlerankl of selectors. .These selectors include theincoming selectors ISI to ISI and a number -of .local selectorsLSltoLSXmy Theconnector CI vis .onejofa number of connectors used togcompletecalls to lines of theiirst hundred, of 'which the line ofthe illustrated; substation is'one..` The lines. otthis hundred are also accessible to. a number of finders, iof which the nder FI is one. The nder FI is linked individually tor thelocal selector LSI, each of the other line nders beingsimilarly linked respectively withlocalselectors.

The rst three levels of all ofthe selecto-rs may be multipled straight through as indicated, and extended to the connectorsserving the respective hundredsgroups. l f y The vfourth level of the ylocal selectors ALSI to LSX is unused or deadfllwhile the; fourth level of theincoming vselectorsvIS'l toIS givesaccess to one or more second selectors SS. yThe second selector vSS has access, through the rst three l levelsr thereof -to verication connectors,y one `of which may be provided in each hundreds group` in accordance with the'usual practice, enabling a toll operator` to make connection with a busy `line to 'thus verify anyindicatedbusy-condition.

The `iifth'to seventh 'levels of all of thesel'ectors are at present unused. A. 'f

The eighth levellof thelocal selectors LSIto LSX is `unused'or deadj while, the eighth/level of the incoming selectorsgives access to theoutgoing-branch'rof'the 13011 line` TLS of Fig. ex..

locatedl outside the system and interconnected with tandem exchange Bby tou unes TLI to TL3. Exchange A contains Va long-distance toll board, Vand may have toll lines,` such as TLG and TLT,

tending between exchanges` B and DI.. A

The ninth eVel l0.f the local selectors lsu 551er fdeadf whue the ninth ievei ofthe' incoming selectors gives access to the outgoing'brarich 30;@

of toll line TL4 of Fig. 1, extendin-gbetween ex changes B and C.

The tenth level of the local selectors gives access to trunk lines leading to jacks J3 to J5 at the local toll board, by way of call switchers CS3 to CSS.

The tenth. (Il)v level of the incoming selectors gives access, by way of outgoing branches 45| to 453 of tool lines TLI to TLB, respectively, extending between exchanges A and B'.

The outgoing repeaters ORI to OR are associated respectively with the tol-l lines TLI to- TL5. The circuit arrangements of the repeater OR4 are as shown in Fig. 3.

The incoming branches of the toll lines TLTI to TL3 extend respectively to incoming selectors IS-l to ISS, while the incoming branches of the toll lines TL4 and TL5 extend' respectively to tollboard jacks J I and J3, by way of call` Switchers CSI and CS2.

Thefcall switchersCSI to v4C555-` may all besimilar, the circuit arrangements `of the call `switcher CSI being shown in Fig. 4. f

As above indicated", the normally connected outgoing branches of. the call Switchers CSI to.

-CS5 extend respectively to the ljacks J I to J5 at the locall 'toll-boards LTB. The alternate outgoing branchse of the Acall Switchers 'CSI to `C55 may be extended by an automatic trunking operation to be hereinafter described to any idle one of the outgoing branches 45I to 453 of theY toll lines leading to the long-distance. toll board in exchange A.

For thev completion of calls. through the local toll board LTB, four single-plug cords are provided, endingA in theplugs P'Ij to P4. These four cords are associated respectively, through the` local repeaters LRI.to. LR4, with the incoming selectors ISI 'to IS4.` The local repeaters may all be` similar, the circuits ofthe local" repeater LRI beingshown in Fig. 5.

The selectors andconnectors in exchange B can be 4of any' suitable construction vand circuit arrangement, and contollable over the usual loop dialing` circuit. Additionally, the construction 'and circuit arrangements of `the finders such as F may be'of anyfsu'itabletype..

FIGURE. 3

Referring'to Fig. 3, the outgoing repeater OR4 of Fig. 2 includes lthe repeating coil 303, line relay 30|-, and release relay 302'. As indicated in the drawings, andy as previously noted, this repeater is seized for outgoing operation from the ninth level of the incoming selectors, such seizure occurring'over'y the lthree-eoncluctor 'trunk 300. Normally, the two conductors comprising 'toll line 'T134 .extend through lco'ntactsof relay 3132` to the vcorresponding conductors of' branch trunk line 350, incomin'g'to the call switcher CSI,l but are transferred to the outgoing conductorsof the repeater OR4 when the repeater-'is seized.

FIGURE 4` Common switching relay 4I5 is associated with the call Switchers CSI to CS5. When this relay is in normal condition, the automatic selecting portions of the call ySwitchers are conditioned to extend the incoming calls automatically to the long-distance toll board inlexchange A, over one or another of the toll lines between exchanges B and A, but relay 4I5 may be operated over the associated conductor 4 I 6 from the local toll board at any time such local toll board is attended to thereby cause the calls arriving at the call switchers CSI to CS5 to be brought in at the local toll board through the concerned one of the jacks JI to'J5 of Fig. 2.

FIGURE 5 Fig. 5 shows the first of the jacks JI to J5 of Fig. 2, together with its associated line lamp and transfer key K5. Transfer key K5 is to be actuated momentarily by the operator at the local toll board whenever a call received over the associated jack is one intended for a subscriber reached by way of manual exchange B, to thereby cause the associated call switcher to transfer the call in a manner to be Subsequently pointed out.

The plug PI, together with the associated cord circuit. link Eril?. local repeater LRI, trunk 550, and incoming selector ISI of Fig. 2, comprises one of the four call-completing links shown in Fig. 2J through which the operator at 'the local toll board LTB. can complete calls through such local toll board.

The cord circuit associated with the plug PI includes a delayed-call key KI, and a key 'K2 having a dial position and an answering and listening position. The delayed-call. keys of the various cord circuits are used to enable the operator at-the local toll board to set up one or twoy tail-to-tail, delayed-call connections, as will be subsequently described.

The common equipment at the local toll board includesr the operators telephone indicated generally at OT and an operators calling device OCD of the usual dial type.

A local telephone line 5I2 extends to the local toll board and terminates in the contacts of the DETAILED DESCRIPTION The disclosure having been described generally, detailed description of the operation of the disclosed apparatus will now be given.

I. DAY OPERATION For this purpose, it will be assumedthat the operator is in attendance at the local toll board LTB vof Figs. 2 and 4, and that theA day-night key K5 is accordingly in actuated position, maintaining switching relay II5- in operated position over conductor M6.

IAfEchang/e C to archange B f The handling of calls from exchange C to exchange B, over toll line TLlI of Figs. l to 3,will now bedescribed.

mi. calling the 'location operator The calling subscribed in. exchange C .may dial a preassigned number, such as the digit O,"t o cause` the automatic switching; equipment (not the exchange-C end of the toll line TL4. When this occurs, a direct current bridge is closed across the conductors of the toll` line TL4 in exchange C, thereby operating line relay 408 of the call switcher CSi (Fig. 4) over the toll line TL4., through contacts of relay 302 of the repeater OR4, tip and ring conductors of incoming branch 350, and contacts of switching relay 40|.

At the front contact of its lower armature, line relay 408 operates start relay 402. At the front contactof its 'uppermost armature, start relay 402 .applies ground potential (obtained originally through contacts of relays 4|2 and 4|3) to sleeve conductor S of the associated incoming branch 350 yof the toll line TL4, and. consequently to the sleeve conductor S of thev outgoing branch 300 of the toll line. The toll line TL4 and outgoing repeater OR4 are thus ymarked busy to the selectors (ISI lto IST, Fig. 2) having access thereto. 4

At its lower armature, relay 402 applies ground .potential to conductor 42|, thereby grounding conductor 423 Athrough the outer armature and front contact of the operated switching relay 4|5. Ground potential on conductor 423 operates relay4|3A of the tone-control pair, 'through IA2. Answering the call Upon noting the lighted condition of the lamp 50|, the operator at LTB may insert the plug of an idlecord circuit (the plug Pl, for example) into the jack J I. When this occurs, line relay conductors by relays I4|2'and 4|3, to enable the operator to ihearsuch tone. For this purpose the operator is expected to actuate her listening keybefore plugging in.

506 in the local repeater LRI operates, vover the sleeve conductor S of link 500 through dial-position contacts of the key K2, the sleeve of the plug PI, and the sleeve of the jack J The operation of line relay 506 is followed by the operation ofthe slow-restoring release relay 501, whereupon supervisory relays 508 and 409 operate in series over the tip and ring conductors of the links 400 and 500, through the tilp and ring contacts of the jack JI and plug P| Upon operating, relay 409 operates slow-re- I IAB. Clalss tone During the time required for slow-restoring relay 4|3 to restore following the operation of relay 4|2, thefprimary (lower) winding of relayytype transformer 4| l is the sole source of ground 'supply for the' sleeve leadincorningtothecall switcher CSI. Any tone signal impressed on -such lead is accordingly induced in the secondary windinggthen bridged across the" talking 'ico . sired called line.

The above induced-tone arrangement is ofparticular utility in connection with callswitchers CSS to CS5, accessible to local lines, for classidentifying tones may be impressed on the sleeve leads of desired ones of such lines, according to the usual practice. f

The operator at the local toll board LTB may now converse with thecalling subscriber and make any desired record of the identity of the calling substation and of the destination of the call. f

' In the local repeater LRI of- Fig. 5, as a iurther result of the described operation of release relay 501, ground potential is placed on conductor L of the link 500, by way of the contacts of the polarized supervisory relay 5 l 0, thereby lighting supervisory lamp 502.

IA4. Preparing the `incoming selector IA5. 'Extending the connection In order toy extend the connection to the desired line of exchange B, the operator actuates the key K2 from answering position to dial position, thereby restoring the right-hand contacts oi the key and actuating the left-hand contacts thereof. With the lower left-handl contacts of the key K2 actuated, the sleeve conductor Sy of the link 500, over (which line relay 500 of the local repeater LRi 'is controlled, is transferred from the plug and jack ground to a new circuit to ground including the impulse contacts of the operators calling device OCD and contacts of the key'K3. "Following this', the operator actuates ythedial of the calling device OCD in accordance with'the' digits in. the local number of the de- As a result of each operation of the calling device OCD7 a ser-ies of momentary restorations 0f line relay 506 is produced. Slow-restoring release relay 501 remains unaffected'. vAt its upper contacts, linerelay 506 repeats the momentarycalling-device interruptions overI the tip and ring conductors oi' the link 550 to bring aboutthe operation of the associated incoming selector ISi of Fig.' 2, followed by the operation 'of a connector, such as C|,.to complet'ethe connection to the desired line.

Series relay 509 is operated, through contacts of'release relay 501, vat the beginning of each series of restorations of line relay 506, and re- 'mains operated throughout the series. .Relay 509 interrupts the tip and ring talking conductors between the links l50|.'l'and 550 to avoid the transmission back to the calling line of a series of objectionable clicks. At the same time, it shunts'the resistor 5| l, in series with the associated talking condensers, across the tip and ring conductors of link 550 to improve the dialing circuit to theswitches being operated.

Having dialed they digits in the desired numiber,'the operator may reactuate the key K2 from dial position tov answering and listeningposition to enable her to hear when the called subscriber answers. When the dial-position contacts of the key K2 are restored, the holding circuit of line relay 506 is transferred back from the calling device OCD to the sleeve of the plug PI and jack JI.

. It may be assumed that the desired subscribed is the one at substation #190 (Fig. 2). In this event, the first digit dialed is the digit 1, causingl the selector ISI to associate itself with the irst level thereof and to search for an idle connector in the rst hundreds group of lines. It may be assumed that the connector CI is the i'irst one found to be idle and is consequently se- IAE. Answered supervision When the called subscriber responds, the connector CI may cause the current ow over the conductors incoming thereto to be reversed in the usual manner, causing a consequent reversal in the current flow through the polarized supervisory relay 5I0 (Fig. 5). Supervisory relay 5I0 thereupon operates. With supervisory relay 508` being held in operated position (in series with relay 509), supervisory lamp 502 is extinguished to indicate visually that the calling subscriber has answered.

The two subscribers may now converse with each other as desired over the tip and ring conductors ofthe established connection. After noting the time at which conversation began, the operator may restore her key K2.`

IA'I. Disconnect supervision When the two subscribers have finished their conversation, theyy are expected to replace their receivers to permit the established connection to be cleared out.

'I'he first subscriber to replace his receiver causes theA supervisory lamp 502 associated with the plug PI to become relighted as a disconnect signal. The circuit of such lamp is reestablished responsive to the restoration of polarized supervisory relay 5I0 when the receiver is replaced on the called line.

When the calling subscriber replaces his receiver, supervisory relays 409 and 508 restore as a result of the disconnection of supervisory relay 509 from in bridge of the tip and ring conductors, at the upper contacts of line relay 408. Relay 508 closes a multiple point in the circuit of supervisory lamp 502.

At the back contact of its lower armature, line relay 40B.. closes an operating circuit for the high resistance supervisory relay 4I0 over the ring conductor of the established connectionthrough the lowery winding of supervisory relay 50-8. Relay 508 is unable to operate or remain operated over this circuit because of the high resistance of relay 4I0. The operation of relay 4I0 occurs concurrently with the restoration of relay 400 and serves to prevent the restoration of tonecontrol relay 4I2. Relay 4I2 accordingly maintains start relay 40.2. operated after line relay 408 has restored;

'Upon noting the lighted condition of supervisory lamp 502,I the operator at the local toll board LTB may verify that both subscribers have replaced their receivers by actuating the key K2 to listeningy position and uttering the usual challenge.

IAS. Clearing out Upon assuring herself that both subscribers have replaced their receivers, the operator may take down the connection, by removing the plug PI from the jack JI.

In the local repeater LRI, line and release relays, 505 and' 501 restore in sequence, causing the extended portion of the connection to clear out in the usual manner, and exinguishing the supervisory lamp 502.

In the call switcher CSI, supervisory relay 4I0 restores responsive to the removal of the plug PI from the jack JI. Upon so doing, it opencircuits slow-restoring start relay 402 to permit the latter relay to restore after a slight interval. When it restores, relay 402 completes the clearing out of the exchange-B end of the toll line 'I'LILy the originating portion of the connection having cleared out in the usual manner responsive to the receiver being replaced at the calling station in exchange C (Fig. 1).

IB. Long distance toll calls from exchange C The operations involved in setting up a long,- distance toll call originated in exchange C will now be described.

IBI. Calling the local toll operator The calling subscriber in exchange C causes connection to be extended over the toll line'TL4 of Figs. 1 to 3 to the call switcher CSI of Figs. 2 and 4, as previously pointed out. Operations occur as previously described, including the lighting of the line lamp 50|, and the answering of the call at the toll board LTB, as by the insertion of the plug PI into the jack JI.

IB2. Transferring the call to the long-distance toll operator When the local toll operator at LTB (Fig. 4) learns that the instant call is a long-distance toll call, which must be completed through the long-distance toll board in exchange A of Fig. l, she momentarily actuates the transfer key K5 individual to the jack J I, thereby closing a circuit over transfer conductor TR of the link 400 for the upper winding of transfer relay 4I4. Relay 4I4 thereupon operates, locking its lower winding togrounded conductor 42 I, whereby relay 4II is maintained operated after key K5v is restored.

The operator at the local toll board LTB may now remove the plug PI from the jack JI, freeing and clearing out the local repeater LRI and associated incoming selector.

In the call switcher CSI, relays 409 and 4I2 restore successively when the plug PI is withdrawn. With transfer relay 4I4 operated, the restoration of relay 4I2 extends ground potential to conductor 422: from ground through the front contact of the lower armature of relay 402, conductor 42 I contacts of the operated relay 416, conductor 423, iront contact of the rst lower armature of relay M4, and through contacts of relay` 4I2, to conductor 422.

The placing of ground potential on conductor 422 initiates the previously mentioned hunting action of the ca ll switcher CSI. .With ground onr peater ORI, similar tothe repeater OR4 of Fig. 3.

rBs. Trunkihuntmg in CS1 'Ijhe further operation now depends upon .whether the toll line TLI is busy or is idle. If `such toll line-is idle, there -is a battery potential l onthe sleeve conductor thereof eiTective to opergate test relay 403, to thereby prevent the next succeeding hunting relay 405 from operating.

If toll line TLI is busy, there is no idle-indicating battery potential on the sleeve conductor ;of.its outgoing branch 45|. Test relay 403 therefore fails to operate. The operation of hunting relay 404 is now followed by the operation of ,hunting relay 405 over the following circuit: from ground, through the front contact of the rst upper armature of start relay 402, the winding of test relay '403, uppercontacts of relay 403, front contactof the irst'upper armature of relay A404,5 and through the vwinding of relay 405', to battery. VBeing marginally adjusted, as indicated, test relay403 does not operatelin serieswith a relay such as 405.v Upon operating, relay 405', at

its lower armature, locks itself l to. the grounded 'conductor 422, open-circuiting and restoring the rst hunting relay 404. A test connection is now made with outgoing branch 452k of the second fitoll line TL2 of Fig. 2. f l

If the second toll line is also busy,`relay 403 "still fails to operate, as a resultlof which the restoring start relay 402.

succeeding ones of the relays 405 to 401 is prevented.` Ateits lower contacts, relay 403 extends the grounded. conductor 422 to the winding of switching relay whereupon the llatter relay operates.

IB4. Seizz'ng toll Zine TLI line-ismarked busy, and test relay 403 is restored.

At itsfourth andvk i'lfth upper armatures, relay 40| disconnects the tip and ring conductors in in'coming'group 350 from those extending to the 'jack J I and extends them, through contacts of the operated hunting relay 404, to the corresponding 4conducto-rs in group 45|, leading to the outgoingrepeater ORI, Fig. 2. When this occurs, line relay 408 restores and open-circuits the slow- Start relay 402, however, being slow restoring, remains operated until third hunting relay 406 is operated through-con- .v

tacts of the restored relay 404 and conta-ctsof the operated relay 405.

connection is now made with the outgoing branch 453 of the third toll line TLS. .l

If the'third tollv line is alsofbusy, the operation :of the third hunting relay 406 is followedby the l.ciated talking conductor to thereby, informthe calling subscriber of the busy condition;

y y At its lowermost contacts, relay 401 prepares a circuit for momentarily energizing the magnetA of meter 4I1 (when start relay-402 clears out) to record the a1ltrunksbusy condition.

AIn the present example, it maybe assumed "that the first toll line TLI is idle, instead'of .fbeing -busy as previously assumed. In this event, `the described operation of hunting relay .404 results in the immediate operation of test relay v403 over the following circuit; from ground, through the front contact of the first Y' upper armature ofustart relay 402, thewinding of ytest relay 403, back contact of the third upper arma- :ture of` switching relay 40|,"the associated sleeve Relay 406 locks itselfr` tov conductor 422 and restores'relay 405. A test conductor, the front contact of the second upper armature of the operated hunting relay 404, `the sleeve conductor of branch trunk 45|, and thence to battery overthe sleeve conductor (not shown) extending from the outgoingrepeater ORI to the 'associated incoming selector IS1 (Fig. 2). This sleeve conductor is similar to theone intrunk a holding ground potential has been returned over to the extended sleeve lead (the sleeve conductor in group45| to maintain switching relay 40| locked operated.

In therepeater O-RI of Fig. 2, the relay corresponding torelay 30| of therepeater OR4 (Fig. 3), is operated over the tip and ring conductors of the extended connection to thereby operate the associated release relay corresponding to relay 302. The latter relay transfers the tip and ,ring conductorsofv rthe toll line- TLI from the incoming branch (leading to the selector IS1) into connection with the outgoing tip and ring 'conductors of the repeater ORI to cause the longdistance operator in exchange A to be signaled in the usual manner. The release relay in the repeater ORI, corresponding to relay302 of the repeater ORA, grounds the associated sleeve conductor, being the sleeve conductor of group 45| (Fig. 4) to thereby establish a holding circuit for switching relay 40|. By this holding circuit, the call switcher yCSI is maintained in switchedthrough condition, and the toll line TL4 is maintained 'guarded because the sleeve conductor of the outgoing branch 300 thereof is supplied with ground potential through contacts of the operated relay 40|. Resistor 4I8` is maintained disconnected at the back contact of the second upper armature of switching relay 40|.

When the long-distance operator in exchange A answers the"y call, she may extend it in the usual manner to the desired called line, making IB5.' Clearing out When the conversation is terminated 4and the receiver is replaced at the calling substation, the line and release relays in the repeater ORI (corresponding torelays 30| and 302v of Fig. 3) restore. The latter relay removes ground potential from the associated sleeve conductor, being the sleeve conductor in rgroup 45| (Fig. 4). When this occurs, switching relay 40| restores and re- Amoves ground potential from conductor 422 at its lower contacts, whereupon hunting relay 404 restores.

The call switcher CSI is thus returnedk to its normal condition, and idle-indicating battery potential is reapplied from resistor lII, through contacts of relays y40| and'402, to sleeve conductor S in groups350 and 300, marking the toll line TL4 idle in exchange B.

IC. Exchange B to exchange C I The handling of local toll calls from sub-scribers of exchange B to subscribers of exchange C will now be considered. It may be assumed that the subscriber at substation #190 (Fig. 2) desires to converse with a subscriber of exchange C (Fig. l). For this purpose, the subscriber at substation `#190 removes his receiver and dials the digit 0 -assigned as the call number of the local toll board i ICl. Calling the local toll operator When the digit 'is dialed, the selector LSI associates itself with the tenth (O) level thereof, and searches for an idle trunk line of this level. The active trunk lines reached from the 0 level of the local selectors include the three trunk lines incoming to the call Switchers CSS to CSE respectively, Fig. 2. It'may be assumed that the call switcher CS3 is idle and is therefore the one seized. This call switcher thereupon operates as described hereinbefore for the call switcher CSI (Fig. 4) to light the line lamp (not shown but similar to 50|) associated with the jack J 3 '(Fig. 2).

` The operator at the local toll board LTB may thereupon answer the call by inserting the plug of an idle cord circuit into the jack J3. This plug may be plug PI (Figs. 2 and 5) if idle. When this occurs, the relays of the local repeater LRI voperate as previously described to cause supervisory lamp 502 to become lighted and to cause the tip and' ring conductors of the trunk 550 to be bridged, thereby preparing the incoming selector ISI (Fig. 2) for operation in the usual man.-

ner.

IC2. Calling exchange C The operator may now associate her calling device OCD with the cord circuit in use, and dial the digit 9 assigned to exchange C. If the toll line TL4 is idle at the moment, this toll line is `seized by the operator selector ISI over its outgoing branch 300 by Way of the repeater ORA, Figs. 2 and 3. When this occurs, line relay 30| of the repeater OR4 operates over the tip and ring co-nductors of group 300, followed by the operation of release relay 302. At its lower contacts, relay V302 groundsthe associated sleeve conductor to provide a holding circuit for the selector ISI, Fig. 2. Because of the indicated reversal in the tip and ring conductors in group 300, polarized supervisory relay I0 now operates to extinguish supervisory lamp 502 to simulate answeredy supervision. This arrangement is in lieu of reverse-battery supervision through the repeater ORII.

At its upper armatures, relay 302 disconnects the conductors of the toll line TL4 from the incoming branch 350 and transfers them into connection with the (left-hand windings of repeating coil 303. A signal .bridge is thus established across the toll line, through Ycontacts .of Aline relay 30| to prepare an incoming switch for OperatiQn .in the distant exchange C.

rc3. completing the connection `ment thereupon responds to complete connection to the called line in the usual manner. If this line is idle, the usual ringing current is auto.- matically applied, and the talking connection .iis completed when the called subscriber responds.

IC4. Clearing out When the conversation is ended, and the .call-e ing subscriber at substation #190 (Fig. `2) re.- places his receiver, the concerned call switcher CS3 of Fig. 2 operates as described hereinbefore for the call switcher CSI of Fig. 4 to :give disconnect supervision to the operator, by .restoring supervisory relay 508 ,of the local repeater LRI. Supervisory lamp 502 is thereby :lighted as a disconnect signal. I

When the operator withdraws the plug P I of Figs. 5 4and 2 from the jack J .3, the call switcher CS3, acting as described for the call switcher CSI, restores its start relay, such as 40,2, .to thereby remove ground potential from the associated sleeve lead, and permit the `operated local selector LSI and interlinked nder FI to restore, clearing out the connection between the calling line and the local toll board.

A further result of the removal of the plug PI (Figs. 2 and 5) from the jack is the restoration of line relay 506. Line relay 30| of the repeater ORA restores in response thereto, followed a moment later by the restoration of relay 30.2. The vclearingout operation in the distant exchange C is initiated .at the upper contactsof line relay 30I. The incoming selector ISI clears out responsive to the removal of ground potential from the sleeve conductor of trunk vbranch 300 at the lower contacts of relay 302.

ID. Other local toll calls.

From the foregoing description. it is apparent that other local toll calls may be handled in substantiauy the manner described. For example, calls from exchange C to exchange .D are hapdled as follows:

Calls from exchange C to exchange -D arrive over the toll line TLA, and pass through the call switcher CSI to the jack JI, as previously described. The operator l.may vanswer with one or another 0f her plugs PI to P4, and then extend the call over the eighth level of one or anotheliof the incoming selectors ISI to ISII, and through the repeater ORE, to the toll line TL51ead-ing vto exchange D.

`Local toll calls originated `in exchange Darrive at exchange B over the toll line TLB, and pass through the call switcher CS2 to the .jack J2 at vthe local toll board. From this point, they may IE. Other locally originated long-distance calls ycall switcher CSI and the jack J I (Figs. 4 and When the operator actuates the transfer key individual to the associated-jack and removes her plug from such jack, the concerned one of the call Switchers CSI to CS5 operates as hereinbefore described to extend the connection, over one orv another of the outgoingA branches 45| to 453, to the associatedone of the toll lines TLI grounded by contacts of the key KL'to thereby cause the local repeater LRI torespond in the same manner as when the plug PI is inserted into a-jack. Accordingly, line and release relays 506 and501 operate sequentially and the asso. ciated selector ISI (Fig..2) is prepared for op,- eration in the usual manner over conductor 550.

The left-hand contacts of KI kalso bridge the 4asscociated common talking'conductors across the to` TL3 extending to the long-distance switchboard in exchange A.

' IF.f Incoming lone-distance4 calls n Long-distance calls incoming to the local sysv tem, by way of the long-distance toll boardin exchange A, arrive over vone or'another of the toll lines TLI to TL3 (Figs. l and 2).. Thein-l coming branches of, such toll lines extend respectively to the incoming selectors IS'I to IS5 in exchange B. These selectorskmay becontrolled in the usual manner `from the long-distance toll board. vIf, the desired subscriber is a subscriber of exchange B, the incomingfselector is operated into association with the concerned one Yof the first three levels thereof to vmake connection with a local connectonsuch as CI, which is then operated to complete the connection to the desiredlin'e of exchange B'. n n i n n On the other hand, if the call is for local exchange` C or local exchange. D, theI concerned one of the incoming selectors IS5 to IS'I is caused to associate itself with llevel 8 or level .9.thereof to make connection either with thetoll line TL4 extending to exchangeC'pr with the toll line TLS extending to the exchange D, as the case may. be. Following this, the concerned one of ythe repeaters OR4 and yORE is controlled from the long-distance toll board tor repeatthe series r of impulses constituting the remaining digits in lthe number tov cause the connection to be com..

pleted tothe desired linefin the called exchange.

' IGr.y Delayed callsat the local toll board vThe deiay'edcaii key Kl (together with the corresponding keys in the other cords) and the associated equipment enable the operator at the local toll board LTB to set up delayed-call .(tailto-tail) connections. She may set up sucha she completes the other portion ofthe connectip and ring conductors of the cord. The come mon retard coil 503 thereupon provides a circuit for operating supervisory relay 508, through contacts 'of the operated release relay 501.v `Supervisory lamp 502 becomes lighted through contacts of release relay 501 and contacts of the polarized supervisory relay 5 I 0;

- Leaving the delayed-call key KI operated, the operatormay now actuate the key K2 to dial position, andthen operate the calling devicegOCD to cause the connection to vbe set 4up to the desired -line as previously described. When shev completes the di ling of the number, the operator may transfer the key` K2 from dial position to talking position and converse with the subscriber when he answers. She may request such subscriber to wait on the'line while tion. y f

To complete the secondl leg of the delayed-call connection, the operator actuates to the'leftl the delayed-call key of another idle one oi her cord circuits, thereby connecting the tip and rin-geconductors of the latter cord in parallel with the tipv and ring conductors of the cord illustrated 'in Fig. 5, over the common conductors extending between the keys such as KI yand* the'retard coil 503. The second leg of the delayed-call c onnection may then be extended in the same manner cordsinto association with the common talking toll board LTB is provided with a local connection under either of two conditions. First,

ril? the operator has reason to doubt that the calling subscriber has given the `disignation of his own line, she may request him 13o-replace his receiver and wait until he isvcalledback. Second, ifA the called line is ,busy (a true delayed call), the operator. may request the calling subscriber to replace his receiver andwait until he is called back when the called line becomes available.

To originate one leg of a delayed-callconnection over the cord circuit illustrated in Fig. 5, `the operator may actuate the key KI to the left, lwhen the cord is idle, and the plug -PI is consequently not in a jack. When this occurs, the 'sleeve conductor-'associated with -the'.plug PI is as described for the first leg of such connection. When the call over the second leg of the connection has been answered, the two subscribers may converse with each other, as the talking conductors of ther two cords are then interconnected .through the delayed-call keys thereof, both actuated to the left-hand position in association with the conductors leading to retard coil 503.

Ifjthe occasion arises, the operator may set up a second delayed-call connection while the first one' existsthis time actuating. the delayed-call keys of the concerned idle cord circuits to the right to bring theVtalking conductors of such v conductors associated with retard coil 504.

IH. The operators local line n' the operator at the local line SI2. This'line may be one of the local lines equipped for the usual two-way subscriber service, being a line of one of the three hundreds groups of exchange B. The usual substation ringer is bridged As previously noted,

across the conductors of local line 5I2, through contacts of the dial and answer position ofthe key K3, whereby the operator is signaled in the usual manner when called over the local line 5I2..

When the operator answers the local call, yby actuating the lefthand contacts of the key K3, the `usual direct-current answering bridge is placed across the conductors of line 5I2. This bridge includes the operators telephone OT, conf tacts of the key K3 and the impulse contacts of the calling device OCD. When the conversationis terminated, the operator -rnay restore the key K3, freeingthe local line.

When the. operator y`desires to originates. call over local line 5.|2, she may do so by actuating the left-hand contacts of the key K3, thereby bridging her headset conductors across the local line in vseries Iwith the impulse contacts of the calling device OCD. By operating this calling device, the operator may extend the local line in the usual manner. The lower contacts ci` the calling device OCD shunts the Operators telephone during such time as the calling device is in an off-normal position, thereby improving the dialing circuit and avoiding disagreeable clicks in the receiver of the operators telephone.

If, while conversing over the local line 2, the operator must temporarily attend to other duties, she may acquaint the called subscriber of this fact and then transfer the key K3 from dial position to hold position, thereby restoring the left-hand contacts thereof and actuating the right-hand contacts of suchkey. Retard coil 505 is thereby bridged across the local line 5|2 to hold the connection until the operator returns to it and reactuates the key K3 from its righthand position to its left-hand position.

Thelconnection extended over local line 5|2 is cleared out in the usual manner when the operator restores the key K3 to normal position.

H. NEIGHT OPERATION The special arrangements for handling all locally originated toll calls through the long-distance toll board at night, or at other times, when the local toll board is unattended will now be described.

IIA. Initiating night operation To initiate night operation, the operator atthe local toll board LTB restores the day-night key K4 to normal postion, open-circuiting and restoring transfer' relay 4|5. At its outermost'armature, relay 4|5 disconnects conductor 42| -of the call switcher CSi from conductor 423, and transfers it into connection with conductor 422, provided tone-control relay 452 is restored. At Athe same time, the remaining armatures of relay 4|5 make a similar transfer of the corresponding conductors-of the call Switchers CS2 to C85.

If, at the time key K4 and relay H5 are restored to place the call Switchers into condition for night operation, there exists a connection through one of these call Switchers by way of the local toll board, such connection is not thereby for example, conductors 422 and 423 are both open, at the contacts of tone-control relay 4|2, after a call has been answered at the local toll board and supervisory relay 459 has brought about the operationof relay 4|2. But, when the concerned calling subscriber has replaced his receiver and caused disconnect supervision to be given to the operator at the local toll board as hereinbefore described, and the operator has taken down the connection, tone-control relay 4|'2 restores to join conductor 422 to conductor 42|, through the back contact of the outer arma- -ture of transfer relay 4|5. Y f

IIB. Extending locally originated toll calls With common transfer relay 4|5 restored, when the call switcher'CSi of Figs. 2 and 4 is seized, over the toll line TLfl, and relays 443 and 402 operate as previously described, ground potential is placed on conductor 422 over the following circuit path: from ground, through `the Vfront contact of the lower armature of kstart relay 402, over conductor 42|, back contact of the outer armature -of the restored relay 4|5, and the lowermost contact pair of relay 4|2, to conductor 422. The extension of ground potential to conductor 422, with start relay 402 in operatedcondtion, causes the hunting portion of the call switcher (comprising test relay 403, hunting relays 404 to406, and 'busy relay 401) to operate as hereinbeiore described t0 cause the call incoming lto the call switcher CSI to be transferred over an idle one of the outgoing branches to 453,and the corresponding one of the toll lines TLI to TLS ot Fig. 2, to the long distance toll board iii-exchange A (Fig. 1).

If the locally originated toll call is for a line outside of the local system, such toll call may be completed by kthe operator at ,the long-distance toll'bo'ard in the'usual manner.

IIC. Completing local toll calls When the operator at the long-distance toll board receives a call-from the local system, over one of the toll lines TLI lto TL3, and learns that the desired line terminates in one or another of the local exchanges B to D, she may extend such connection to the called line in the desired local exchange by interconnecting the toll line over which the call was received to any other one vof the toll lines TLI to TLS which happens to be idle at the time.

Upon the taking of the last-named one of the toll lines TLI to TLS for use at the long-distance toll board, the concerned one of the incoming selectors `IS5 to IS7 is prepared for operation in 'disturbed Considering the call switcher CSI,

the usual manner. Such selector responds in the usual manner to extend the connection toward the desired line. If thedesired line is one of eX- change lB, the incomingselector is caused to associate itself with one or ranother of the first three levels thereof. llf the desired line is one terminating in either of the exchanges vC' and D, the incoming selector is caused to associate itself with the level assigned thereto. From this point, lthe connection is completed to the desired called line as previously discussed.

IID. Delayed calls Delayed `calls between lines of the local system rnay'be completed through the long-distance toll board vby the setting up of a connection from suchtoll board over one of the vtoll lines TLI to TLS to the called line, and by joining such toll' line with anotherone of the three `toll lines and setting up a connection over the latter toll line to the calling line. This procedure may be used also when the operator at the long-distance toll board has reason to believe that the calling subscriber has not given the designation of his own line, and Arequests him to replace his receiver and wait until called.

IIE. Terminating night operation When 'the operator returns to the local toll board LTBof Figs.r2 and 4 to resume operations ther-eat, she actuates the day-night key K4, thereby operating the common transfer relay 4|5 overconductor 4|6. Each of the call Switchers is thereupon converted from night operation to day operation.

In `the call switcher CSI of Fig. 4, conductor 42| is disconnected from conductor 422 and is transferred into connection with conductor 423. If this occurs during a time when a connection exists through this call switcher over one or another of theoutgoing trunk branches 45| to 453,

vthe vchange-over has no immediate effect, for

conductor 422 is held energized at the lower conf tact pair of the then operated switching relay 40|, and there is no energizing potential on conductor 42|, for start relay 402 is then in a restored condition. I

Upon the clearing out of the above-noted connection existing through. call switcher CSI, `reswitching equipment controllable over calling lines thereof to set up connections therefrom to called lines thereof, other telephone exchanges,

a local toll board, means veffective when asubscriber of any local exchange desires a connection with a line other than a line of such exv change for extending connection from the calling line to said local toll board, means atsaid local toll board for extending such connections therethrough and by way of automatic switching equipment to desired called lines of said local exchanges, means including a long-distance toll board for completing toll connections to lines of said other exchanges; and means controlled from said local toll board, when a call received thereat is intended for one of said other exchanges, for completing a connection from the calling` line to said long-distance toll board in by-pass of said local toll board.

2. In a telephone system, a group of local telephone exchanges each including automatic switching eqpipment controllable over calling lines thereof to set up connections therefrom to called lines thereof, other telephone exchanges,

a local toll board, means effective when a subscriber of any local exchange desires a connection with a line other than a line of such exchange for extending connection from the calling line to said local toll board, means controlled from said local toll board for extending such connections by way of automatic switching equipmentto desired called lines of said local exchanges, means including a long-distance toll board for completing toll connections to lines of said other exchanges; and means controlled from said local toll board, when a connection is extended thereto pursuant to a callto a line of one of said other exchanges, for extending a branch connection therefrom to said long-distance toll board. f v

3. In a telephone system, two exchanges, an operators switchboard associated with 'the rst exchange, links incoming to said` switchboard,

means for extending connections from calling lines of the rst exchange over said links respectively to said switchboard, separate switch-l ing means associated individually with said links and controllable by the operator at said switchboard, and means responsive to the actuation of the said switching means associated with any link over which a connection has been extended to said switchboard for diverting such connection from the operators switchboard to the second exchange.

4. In a'telephone system, two exchanges, Aan operators switchboard associated with the iirst exchange, links incoming to said switchboard,

means for extending connections from calling lines of the first exchange over said links respectively to said switchboard, switching means common to said links and controllable by the operator at said switchboard; and means responsive vto the actuation of the said` switching means for diverting, from the operators switchboard to the second exchange, connections incoming over any of said links.

5. In a switching system, an operators switchboard, a call switcher, a trunk line incoming to said call switcher, a rst outgoing trunk line extending from said call switcher to said switchboard, other outgoing trunk lines extending from said call switcher to another destination, control means associated with said switcher and ca` pable of assuming two positions, means responsive to the control means being in one position for extending a call received over said incoming trunkl line over said first outgoing trunk line to the operators switchboard, and means responsive to said control means being in the other position when there is a call incoming to the call switcher for selecting an idle one of said other outgoing trunk lines and for extending the call f thereover.

6. In a switching system, an operators switchboard, a call switcher,I a trunk line incoming to said call switcher, a rst outgoing trunk line extending from said call switcher to said switchboard, other outgoing trunk lines extending from said call switcher to another destination, control means associated with said switcher and capable of assuming two positions, means responsive to the control means being in one position when a call is received over said incomingk trunk line for extending such call over said rst outgoing trunk line to the operators switchboard, and means responsive to said control means subsequently assuming the other position for selecting an idle one of said' other outgoing trunk lines and for extending said received call 'thereoven PIER BAKKER.

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